State changes in Mediterranean ecosystems

Abstract

Wildfire activity is increasing due to climate change as are global temperatures and drought. Mediterranean ecosystems are highly prone to wildfire and when disturbance is large enough state shifts can occur including deforestation. Plant types have different responses to disturbance: Seeders perish but regenerate from seed banks while resprouters can survive and generate new shoots from dormant buds. In this thesis, transitions between different vegetation types based on these fire response strategies are analyzed in the San Francisco Bay area. SPSS analysis were conducted using vegetation data from 1940 and 2010 as well as data on large wildfires, altitude and local climate to determine possible correlations between these variables. Significantly more state transitions occurred in areas where wildfire was present compared to where it was not. Additionally, succession from shrubland to resprouter forest occurred less often under the influence of wildfire. In general the results show state transitions in mediterranean ecosystems to be complex processes affected by a large variety of factors. Mediterranean ecosystems are likely to respond to increases in wildfire activity and more vegetation change is expected to occur in the face of increasing climate change. Future research using more detailed vegetation and wildfire data over larger time scales will provide more insight into the dynamics of vegetation and wildfire.